The present invention relates to a marine, flexible, integrated umbilical (for control, injection or production), which umbilical comprises a number of fluid flow pipes and optionally electric conductors, filler material between the fluid flow pipes and the possible electric conductors, which filler material comprises several inner and outer channel elements that are twisted about the longitudinal axis of the umbilical and are assembled such that they form channels for receipt of the fluid flow pipes and the possible electric conductors, said pipes and conductors being axially free movable within the channels, and an outer sheath of suitable material.
Complete umbilicals of this type and how they are manufactured are disclosed in WO93/171776.
Such umbilicals are designed for subsea use to transfer fluid, and optionally electric energy, hydraulic liquid and electric signals one or both ways. As used here the term “umbilical” is intended to encompass a flexible or bendable bundle of pipes and cables that includes a plurality of transfer lines like electric conductors, both for energy and signals, and fluid flow pipes, both for liquid and gas.
Such fluid flow pipes will typically be of smaller diameter and made of steel, and may, as an example, be used for high pressure hydraulic liquid to actuate equipment, like valves, on the seabed. Traditionally they further include a central steel pipe of larger diameter for transportation of larger amounts of liquid, like methanol, for injection into a gas or oil well. One or more of the flow pipes can also be used for chemicals to be injected into a formation or return of “used” liquid. In an alternative embodiment the central steel pipe may be replaced by a load carrying element, such as a steel wire.
Umbilicals of this type are exampled and disclosed in the above mentioned publication. It is, however, not decisive that the umbilical comprises electric conductors in the transversal cross section and it is conceivable as a bundle of pipes, possibly with a centrally located pipe of substantial dimension for transportation of produced oil and gas to the surface in the same way as a riser. Such a flowline, or production tubing, is termed IPU™ (Integrated Production Umbilical).
An early use of such umbilicals was between a surface vessel and a submerged remote operated vessel (ROV).
A need has existed to improve the impact resistance of the outer sheath of the umbilical, which is normally made of a plastic material.
Moreover it has been common that such umbilicals include weight elements merely to ad sufficient weight so that they shall not become buoyant. The weight elements have usually been made of lead and have been integrated into the umbilical as part of same. Naturally this has provided substantial additional costs to the umbilical.